Embodiments of the present invention relate to voltage controlled oscillators. In particular, the present invention relates to a highly accurate voltage controlled oscillator that exhibits optimal performance across a wide range of frequencies.
Voltage Controlled Oscillators (VCOs) are per se known. VCOs generate an oscillating signal at their output that varies in frequency according to the level of voltage input. VCOs are widely applied in high speed clocking applications such as clocking circuits and within phase locked loops (PLLs).
Conventional VCOs offer performance at less than an optimal duty-cycle of 50% across a wide range of frequencies. As frequency increases, the duty-cycle of traditional VCOs approaches 100% causing traditional VCOs to fail prematurely. Thus, traditional VCOs suffer from limited use at the higher frequency ends and utilize power inefficiently.
To maintain an optimal duty cycle, traditional VCOs are required to operate at twice the desired output frequency. An output at 50% duty cycle can then be obtained by halving the frequency of the poor duty cycle output from traditional VCOs. This technique is disadvantageous in that running the VCO at twice the required output frequency significantly increases the power consumed and halves an unstable maximum operating frequency. At higher frequencies, traditional VCOs become unstable due to the inherent non-symmetry in their design.
There is a need for a VCO that oscillates at or near the optimal duty-cycle of 50% across a wide range of frequencies. There is also a need for a VCO that is more accurate and stable at higher frequencies, and that offers reduced power consumption.